It is known from practice that material webs, especially those consisting of fibers, are needled for strengthening and for producing material structures in a process step. The material web is guided for this continuously into a needling zone, in which oscillatingly driven needles of a needle bar penetrate the material web. The material web is drawn out of the needling zone by a drawing apparatus, e.g., by a plurality of drawing rollers. A drawing speed set by the drawing apparatus now becomes established on the material web. Due to the needles penetrating into and being removed from the material web, it is not possible to carry out the passage of the material at the drawing speed determined by the drawing apparatus. The drawing apparatus therefore generates more or less pronounced drawing forces, which affect the structure of the material web, depending on the motion of the needles.
To keep this effect as minimal as possible, a method and a device for a continuously fed material web is known from U.S. Pat. No. 5,909,883, in which the drawing rollers of a drawing apparatus are driven at a modulated angular velocity, so that a lower drawing speed prevails during a phase during which the needles engage the material web. The insertion cycle and the modulation are coordinated with one another for this, so that the interaction between needling and the drawing apparatus can be reduced.
However, the prior-art method and the prior-art device have basically the drawback that, on the other hand, higher production speeds are not feasible and, on the other hand, the drawing speed of the material web has insufficient constancy for subsequent process steps.
To make it possible to reach higher process speeds, methods and devices are used in the state of the art for needling a material web in which the motion of the needles generate a superimposed horizontal feed on the material web. Such a method as well as such a device are known, for example, from WO 2008/51961 A1. The bar carrier is driven here via a vertical drive and at the same time via a horizontal drive such that the needles are guided on an elliptical guide path, which generates a horizontal stroke and on the material web during each insertion cycle. The size of the horizontal stroke can be set by setting the guide path of the needles. Thus, it is possible to generate a material throughput with a material speed that leads to reduced drawing of the material by the drawing apparatus relative to the drawing speed by setting a correspondingly high insertion frequency and a large horizontal stroke. However, it was found as the production speeds were increased that even small changes in the setting of the horizontal stroke have led to superproportional changes in the drawing of the material by the drawing apparatus. In addition, the initial settings of the horizontal stroke can be preset only on the basis of empirical values, which make a subsequent optimization of the horizontal stroke inevitable. Adjustments of the machine settings by the operators are therefore often necessary.
Furthermore, it is known from DE 103 46 473 A1 that the passage of the material can be controlled as a function of the pattern to produce a pattern in a material web. An electronic camera, which observes the material web and is coupled with a control means for controlling a drive for moving the needles, is provided for this in an intake zone. Zones with and without needling can thus be produced.